The settings you choose via the admin area should remain when you update the theme and this plugin, even without a child theme. Those settings are stored in the database, so they should not be overwritten as part of an update. However, if you wish to make any other customizations beyond the settings available through this plugin, you should create a child theme.
Personally I recommend always creating a child theme, even if you just create CSS and functions.php files that contain nothing more than the minimum code called for in the WordPress child theme creation documentation. That way, you already have a child theme in place if you ever discover the need to add some additional customizations in the future.
